The James Webb Space Telescope will be 100 times more potent than Hubble, and will launch in 2018 on a mission to give astronomers an unprecedented glimpse at the first galaxies that formed in the early universe.

"JWST will be able to see back to about 200 million years after the Big Bang," NASA said on its website.

It described the telescope as a "powerful time machine with infrared vision that will peer back over 13.5 billion years to see the first stars and galaxies forming out of the darkness of the early universe."

The project has drawn scrutiny from lawmakers for its ballooning costs -- now at about $8.8 billion, far higher than the initial estimate of $3.5 billion.

But NASA has promised to keep the next-generation telescope on track for its October 2018 launch.